1. Field of the Invention
This invention relates to a rotary element driving device for rotating a rotary element such as a 3.5" floppy disk, optical disk, or polygon mirror.
2. Description of the Related Art
A rotary element driving device of this type (fur rotating a rotary element such as a 3.5" floppy disk, optical disk, or polygon mirror) is known in the art. The device has a spindle motor to rotate a rotary element such as a floppy disk, optical disk or polygon mirror.
In installing the spindle motor in the rotary element driving device--for instance in assembling a disk drive device for rotating a 3.5" floppy disk, the necessary components are not directly set in the disk drive device to form the spindle motor. Rather, the following method is employed: As shown in FIG. 5, a spindle motor 35 is formed separately from a disk drive device stand 37, and the former 35 is mounted on the latter 37. This is because, in general, a manufacturer forming the motor is different from a manufacturer who forms the disk drive device.
The spindle motor 35, which is formed separately from the disk drive device stand 37, generally comprises: a rotor casing 33; a hub stand 36 which is formed embossed together with the rotor casing 33 so that a floppy disk (or magnetic disk) is mounted on it; a stator (not shown) built in the rotor casing 33; and a motor driving circuit board 31 provided integral with the stator. The circuit board 31 has mounting holes 31a which are used to mount the spindle motor 35 on the disk drive device. With the mounting holes 31a aligned with mounting holes (not shown) formed in the disk drive device stand 37, screws 32 are threadably inserted into those mounting holes to fixedly mount the spindle motor 35 on the disk drive device.
The circuit board 31 of the spindle motor is liable to warp because it is made of a thin-plate-shaped material. If, with the circuit board 31 warped, the spindle motor 35 is mounted on the device stand 37, then the hub stand 36, on which a disk is mounted, is unstable in height; i.e., the spindle-motor mounting surface of the device stand 37 and the disk placing surface 36a of the hub stand 36 are lowered in the degree of parallelization. Accordingly, the recording and reproducing head adapted, for instance, to read data from the disk, and the disk placed on the hub stand 36 are lowered in positional accuracy, as a result of which errors are liable to occur during data reading or writing operations.
The same thing may be said about the case where, instead of the disk, a polygon mirror is employed. If, with the circuit board 31 held warped, the spindle motor 35 with the rotary element, namely, the polygon mirror is mounted on the drive device stand 37, then the polygon mirror is changed in height, or inclined, as a result of which it is impossible to move the laser beam along the predetermined optical path. Thus, the rotary-element driving device is insufficient in accuracy.